ABSTRACT The goal of this K23 Mentored Patient-Oriented Research Career Development Award is to broaden the candidate?s expertise in sleep disturbance and neurocognition in adolescents with Attention- Deficit/Hyperactivity Disorder (ADHD). ADHD in adolescence is frequently predictive of detrimental academic and social outcomes. In part, poor functioning may be due to neurocognitive deficits observed in ADHD; however, the extent of these deficits is variable and the mechanisms contributing to greater impairment in some individuals and not others are poorly understood. Sleep disturbance represents one potential contributor to the neurocognitive abnormalities observed in a subset of youth with ADHD. Specifically, disturbed sleep is prevalent in ADHD and there is considerable overlap between core ADHD features and the neurocognitive correlates of sleep impairment. However, associations between sleep physiology and variable clinical and neurocognitive outcomes in ADHD youth have yet to be investigated. Training objectives for the proposed K23 will include gaining expertise in advanced laboratory-based administration, scoring, and analysis of polysomnographic data, assessment of neurocognitive and clinical correlates of sleep impairment in ADHD, and enhanced understanding of developmental trajectories of sleep function in typically developing and ADHD adolescents. These objectives will be met through mentoring, research, and coursework, which will result in an independently funded program of research to elucidate the biological mechanisms underlying sleep problems and neurocognitive impairment in ADHD and develop innovative sleep-based interventions targeting core symptoms in this population. Dr. Scott Kollins, the primary mentor for this application, has a strong record of clinical research assessing clinical and neurocognitive outcomes in ADHD. He is the director of the established research training site where the applicant will be trained. The research plan involves using polysomnography to assess sleep disturbance and neurocognitive outcomes in adolescents with ADHD and healthy controls (HC). The primary hypothesis predicts that adolescents with ADHD will display reduced duration, increased latency, increased nocturnal awakenings, reduced delta power, and disrupted sleep spindles compared to HC. Variability within groups is predicted, and we will explore whether there are distinct subgroups with and without sleep problems within the ADHD group. In addition, sleep disturbance is predicted to be associated with poorer neurocognitive and clinical presentations in ADHD adolescents. If these hypotheses are supported, sleep disturbance may represent a biomarker for phenotypic subtypes of ADHD. In addition, examining this construct may inform development of prevention and intervention strategies with the potential to impact sleep disturbance as well as core symptoms of ADHD in adolescents.